"I believe so, but no matter," he said, "I go by Cephei."

The 'I go by' rather than 'my name is' should be enough of a tell that he couldn't lie and therefore was fae, if she was familiar with his kind.

"And what I told her was that the enemy of my enemy is my friend, so to speak. I know there have been tensions between your sort and mine in the past, but fighting between us when a larger threat looms would hardly be sensible."